1. Field of the Invention
The present invention relates to automated testing systems and methods that perform at-speed testing of high serial pin count devices that transmit serial data at gigabit per second baud rates.
2. Related Art
Traditional testing systems for semiconductor devices employ automated testing equipment (ATE). Today, high-speed (e.g., gigabit per second (Gbps) baud rate) semiconductors can be quad serial data input/output (I/O) port (having 4 serial data pins per port coupled to 4 transmit/receive differential pairs) stand-alone physical layer devices (PHY's) or high port count integrated application specific integrated circuits (ASIC's), switches, or backplane transceivers. Most ATE's become perpetually outdated in terms of being able to perform at-speed testing (testing at the rated speed of the semiconductor device) of high speed devices with high serial pin counts. Presently, two main ATE's performing tests on high speed high serial pin count devices are the Teradyne Tiger and the Agilent 93000 test platforms that can deliver 1.25 Gbps on standard single ended channels, where Teradyne can deliver 1.6 Gbps differential channels and Agilent can deliver 2.5 Gbps differential channels. Aside from these ATEs, specialized high-speed test options can cost hundreds of thousands of dollars and usually offer very limited functionality.
Aside from automated testing systems, non-automated testing equipment systems utilize “serial external loopback” (device transmitter connected directly to device receiver) configurations for at-speed testing (testing at the rated speed of the semiconductor device). There are also some single channel ATE instruments, such as digitizers and sine wave sources, as well as bench instrumentation with a few channel capability, such as bit error rate testers (BERTs), that can be used to test some semiconductor devices. Unfortunately, these testing systems are only effective for semiconductor devices with a very small number of serial data pins and channels. This is because it can be difficult to route many devices with a high number of serial data pins to a single ATE source or capture instrument due to limit device interface board (DIB) space allowed for application circuitry on test heads. Also, bench instrumentation are an expensive upgrade solution to an ATE and typically are not production worthy. Further, test time, which contributes to the cost of testing, is very high on bench instrumentations because they are not designed for automated production testing.
To overcome some of these problems, other systems have utilized a golden device concept. In these systems a same or complementary functioning semiconductor device as the device under test (DUT) is used as a golden device to test itself. For example, when the speed of a serializer is too fast for an ATE then a deserializer can be used to bring down the speed into a range in which the ATE can test. However, the use of the golden device becomes nontrivial when the serial data pin and channel count of a DUT increases. This is because the test complexity is compounded by the need to have connections to the golden device, external loopback devices, and analog instrument device for signal routing on one DIB, which makes the signal delivery or signal routing too complex to design for high serial pin counts.
Consequently, a result of all these problems has been a dramatic decrease in at-speed production test coverage. This has both lowered the quality of semiconductor devices and raised the rate of field defects and failures.
Therefore, an ATE is needed that is capable of at-speed testing of multiple Gbps and higher semiconductor devices with high serial pin counts that can be easily adapted to keep up with the constantly changing device speeds and configurations and that will be small enough to fit in the limit real estate available on a DIB. There is also a need for the ATE to have low capital costs for upgrades.